Isolation and characterization of the protease-activated form of pyruvate oxidase. Evidence for a conformational change in the environment of the flavin prosthetic group.

摘要: Abstract Pyruvate oxidase is a tetrameric enzyme consisting of four identical subunits. The specific activity the may be increased more than 20-fold by limited proteolytic digestion alpha-chymotrypsin in presence pyruvate and thiamin pyrophosphate. This "activation" phenomenon due to cleavage an Mr = approximately 2000 peptide from each subunit. "activation peptide" (alpha) readily separated activated high performance liquid chromatography under nondenaturing conditions. alpha not required maintain modified tetramer state. Cleavage monomer directly correlated with substantial change visible spectrum flavin, characteristic shift hydrophobic hydrophilic environment. Proteolytic absence pyrophosphate irreversibly inactivates at different site, producing 9000 "inactivation (beta). beta remains noncovalently associated inactivated tetramer. does alter even though contains sequence. These results suggest that release opens up flavin active site responsible for observed stimulation enzymatic activity.